Skin TRPA1 ion channel participates in thermoregulatory response to cold. Comparison with the effect of TRPM8

There was no clear evidence of the TRPA1 ion channel involvement in the formation of thermoregulatory responses. The present results convincingly show that the skin TRPA1 ion channel activation has significant influence on the formation of thermoregulatory responses of the body to cooling; it is especially strongly manifested for the metabolic component. At the TRPA1 activation by its agonist AITC (0.04%), an enhancement in thermoregulatory responses is observed: the temperature thresholds for the first phase and the second one of the metabolic response decrease, the values of all components of the metabolic response considerably increase: the increment of oxygen consumption in the first phase increases from 1.8 +/- 0.24 in the control to 2.9 +/- 0.35 ml/min*kg under AITC, P = 0.04; the increment of oxygen consumption in the second phase increases from 6.2 +/- 2.06 to 17.4 +/- 1.20 ml/min*kg, P = 0.002, as well as shivering rises from 7.8 +/- 1.79 to 15.4 +/- 1.87 mV, P = 0.011. In consideration of our previous results on the influence of TRPM8 ion channel activation on thermoregulatory responses (Kozyreva et al., J. Therm.Biol., 2010) it is obvious that the TRPM8 and TRPA1 ion channels have a pronounced, but unequal effects on the values of different phases of the metabolic response to cold. The TRPM8 activation manifests itself in an increase of value only the urgent first phase, this phase is associated with carbohydrate metabolism. As the recent results have shown the influence of the TRPA1 activation is realized predominantly in the clearly marked increase in the second phase of the metabolic response associated with lipid metabolism, as well as in evident shivering gain. The ability to predominantly control different parameters of thermoregulatory responses to cold may indicate the importance of both the TRPM8 and the TRPA1 ion channels in the processes of maintaining temperature homeostasis. The obtained data testify to the joint sequential operation of these thermosensitive ion channels.